A metal ion secondary battery (for example, a lithium ion secondary battery, and also referred to as an “all-solid-state battery” in the following description) having a solid electrolyte layer obtained by using a nonflammable solid electrolyte has many advantages such as easiness to simplify a system for guaranteeing safety.
As a technique for such an all-solid-state battery, for example, Patent Literature 1 discloses a method for producing a sulfide solid electrolyte material including a microparticulation process in which an ether compound is added to a coarse-grained material of a sulfide solid electrolyte material, and the coarse-grained material is microparticulated through a pulverization treatment. In paragraph [0031] of Patent Literature 1, it is described that the coarse-grained material may contain an element X (where “X” denotes a halogen element). In addition, in paragraph [0027] of Patent Literature 1, it is described that the amount of the added ether compound may be set to, for example, 0.01 to 100 wt % with respect to the coarse-grained material. Furthermore, in paragraph [0044] of Patent Literature 1, it is described that a solvent may be added in addition to the ether compound, and the amount of the added solvent is not particularly limited. In Example of Patent Literature 1, it is described that a weight percentage of the solvent with respect to a total sum weight of the coarse-grained material, the ether compound, and the solvent is set to 78% or higher. Moreover, in paragraph [0050] of Patent Literature 1, it is described that a heat treatment process may be performed after the microparticulation process or after the drying process for removing the ether compound following the microparticulation process.